At time of press, this ancient city, a crossroads of civilization, thought to date back over 8,000 years, is off-limits to most tourists. Once a gem of the Middle East, the fortress overlooking modern Aleppo is partly destroyed owing to the ongoing Syrian civil war.

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Burrup Peninsula, Australia

Murujuga, also known by the modern name Burrup Peninsula, in northwestern Australia, is home to potentially the world’s oldest and most endangered petroglyphs. Some of the more than one million images are more than 40,000 years old.

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Erbil Citadel, Kurdistan, Iraq

Among the oldest continually inhabited areas on Earth, this walled settlement looming over modern Erbil, in Iraq’s northern Kurdish region, shows signs of occupation dating to the fifth millennium B.C. It is among the newest UNESCO sites, inscribed in 2014.

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Göbekli Tepe, Turkey

Built beginning in the tenth millennium B.C., Göbekli Tepe seems a re-creation of paradise, with stelae carved in images of exotic plants and animals. Now in a desert, the giant temple complex is thought by some to be the inspiration for the biblical Garden of Eden. Ancient human figurines have been found.

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Cave of El Castillo, Spain

The oldest known paintings in the world are in the Cave of the Castle, in Cantabria in the north of Spain. Thought to be more than 40,000 years old, many of the images are stencils of ancient hands made by artists blowing paint from their mouths.

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Lascaux Caves, France

Over 2,000 images of horses, cows, cats, birds, and their human hunters seem as vivid today as when they were painted in these caves more than 17,000 years ago. Discovered in 1940 in what is today southwest France, the cave is closed to the public, but a replica is open for visitors.

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Potok Cave, Slovenia

Cro-Magnon people—the first anatomically modern humans—found shelter in this central European cave complex, using the nearly 23,000 feet (7,010 meters) of limestone tunnels as a ritual site or hunting station some 36,000 years ago in what is modern Slovenia.

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Jericho, Israel

Jericho’s walls came tumbling down, and their ruins are the major tourist venue in this West Bank city established perhaps 11,000 years ago, among the oldest inhabited sites in the world. A nearby cable car takes visitors west to the Mountain of Temptation, where Jesus is said to have been tempted by the devil.

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Ġgantija Temples, Malta

Somewhere around 3600 B.C. the ancient temples of Ġgantija were built on Gozo Island in Malta, among the oldest Neolithic structures in the world. They are thought to be dedicated to the Great Earth Mother goddess and, legend says, constructed by giants.

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Skara Brae, Scotland

Inhabited more than 5,000 years ago, the Neolithic town of Skara Brae flourished on Mainland, the largest island in the Orkney archipelago. Strong storms in 1850 led to its discovery, revealing intricate stone roofs, ceremonial structures, and even furniture.